Our invention relates to voice analysis and, more particularly, to speaker verification and identification arrangements.
It is often desirable to identify an individual or verify an asserted identity from voice characteristics. Commercial transactions conducted over telephone facilities are expedited when a party can be identified immediately without resorting to documents or prearranged codes. Similarly, controlled access to secured premises is facilitated by the use of voice identification techniques. Prior automatic speaker recognition systems have been based on the comparison of a predetermined spoken message with a previously stored reference of the same or similar message, or a comparison of selected speech parameters of particular utterances with stored parameters of a corresponding utterance. Combinations of pitch period, intensity, formant and other speech characteristics have been utilized for speaker recognition.
In one type of system such as disclosed in U.S. Pat. No. 3,466,394 issued to W. K. French on Sept. 9, 1969, selected peaks and valleys of successive pitch periods are used to obtain characteristic coordinates of the voiced input of an unknown speaker. These coordinates are selectively compared to previously stored reference coordinates. As a result of the comparison, a decision is made as to the identity of the unknown speaker. This arrangement as well as others relying on particular speech characteristics require that the characteristic coordinates be normalized to prevent errors due to variations in the individual's speech pattern.
Another type of arrangement, such as disclosed in U.S. Pat. No. 3,700,815 issued Oct. 24, 1972 to G. R. Doddington, et al and assigned to the same assignee, compares the characteristic way an individual utters a test sentence with a previously stored utterance of the same sentence. The comparison is restricted to a prescribed sentence and requires that the two utterances be temporally aligned by time warping so that a valid comparison may be made.
U.S. Pat. No. 4,032,711 issued on June 28, 1977 to M. R. Sambur and assigned to the same assignee, discloses an arrangement in which each utterance is filtered to obtain parameters that are highly indicative of the individual but are independent of the content of the utterance. Consequently, it is no longer required to compare utterances of the same phrase for speaker recognition. The statistical parameters that are utilized, however, are not useful for recognition of the contents of the utterance.
U.S. Pat. No. 4,181,821 is issued to Frank C. Pirz and Lawrence R. Rabiner, Jan. 1, 1980 and assigned to the same assignee discloses a word recognition system in which speech patterns of many individuals are clustered to derive a small number of templates for each word. The set of templates are representative of the general population so that the utterances from a broad range of any individuals can be recognized. The linear prediction template parameters utilized for speaker-independent recognition are adapted to recognize the information in speech patterns applied thereto. In many applications, it is important to simultaneously determine both the speaker and the utterance that is spoken. In telephone credit card transactions, for example, identification of the speaker on the basis of his voice characteristics assures that the transaction being recognized by an automatic word analyzer is properly authorized. The concurrent use of the same speaker independent speech parameters for word recognition and speaker identification or verification improves the service rendered and makes the speaker recognition more economical. It is an object of the invention to provide improved speaker recognition in combination with spoken word analysis systems.